This invention relates to a separate lubricating system for marine propulsion device and more particularly to an improved lubricating system for a two-cycle engine, and particularly that of an outboard motor.
With two-cycle internal combustion engines, it has been the general practice to lubricate the engine by mixing lubricating oil with the fuel mixture. Although such arrangements offer extreme simplicity, the mixing of lubricating oil with the fuel can be troublesome to the user of the engine. In addition, the requirement for mixing lubricant with the fuel and lubricating the components of the engine with the fuel/air mixture does not always insure the adequate amount of lubrication to the various components to be lubricated under all running conditions. In order to obviate some of these difficulties, it has been proposed to provide a lubricating system where the lubricant is contained within a separate tank from the fuel and is supplied to the engine during its running. Such arrangements have a number of advantages.
When the engine in question constitutes the power unit of an outboard motor, however, the provision of such separate lubricating systems can give rise to certain problems. Due to the relatively compct nature of an outboard motor, it is difficult to provide the necessary lubricant storage capacity within the confines of the motor. That is, it is desirable that the lubricant system contain sufficient lubricant for long running periods. However, it is difficult to provide an adequate lubricant storage system within the cowling of an outboard motor for such extended running periods. Although these problems may be overcome through the use of a lubricating system wherein the lubricant is stored externally of the engine, such external storage systems themselves give rise to certain problems. For example, it is necessary to deliver the lubricant from a remote location to the engine immediately upon startup and even during cranking so as to ensure adequate lubrication during this extremely critical running condition. Such remotely positioned lubricant tanks, however, make it difficult to ensure adequate lubrication during startup. Therefore, it has been proposed to use a lubricating system wherein the engine mounts a relatively small lubricant delivery tank and lubricant is delivered to this lubricant delivery tank from a remotely positioned lubricant storage tank. An arrangement is provided wherein a substantially constant head of lubricant is maintained in the lubricant delivery tank so as to ensure adequate lubrication under all running conditions. An example of such a lubricating system is shown in U.S. Pat. No. 4,403,578, entitled "Separate Lubricating System For Outboard Engine", issued Sept. 13, 1983 in the name of Tomio Iwai and assigned to the assignee of this application. Although systems of this type have great utility and overcome many of the disadvantages of prior art two-cycle engine lubricating systems, still further improvements are desirable. For example, it is desirable to provide a system wherein a warning is given to the engine operator if the amount of lubricant in the storage tank falls below a predetermined amount so that the lubricant in the storage tank may be replenished.
It is, therefore, a principal object of this invention to provide an improved lubricating system for a two-cycle internal combustion engine.
It is a further object of this invention to provide an improved lubricating system for an outboard motor that embodies a remotely positioned lubricant storage tank and an engine-mounted lubricant delivery tank with a device for transferring lubricant from the storage tank to the delivery tank and further including means for providing a warning when the amount of lubricant in the delivery tank falls below a predetermined value.
In addition to providing a warning when the amount of lubricant in the storage tank falls below a predetermined amount, it is also desirable with lubricating systems of this type to provide some means for insuring against the complete depletion of the amount of lubricant in the system during long cruising periods.
It is, therefore, a still further object of this invention to provide an improved lubricating system for a two-cycle engine in which the depletion of lubricant from the separate lubricating system can be avoided during long running periods.
It is a further object of this invention to provide a system for reducing engine speed to conserve lubricant when the amount of lubricant in the separate lubricating system falls below a predetermined value.
As has been noted, there are a number of advantages in providing a separate lubricating system for an internal combustion engine of the two-cycle type that employs a relatively small lubricant delivery tank mounted on the engine and a larger lubricant storage tank that is remotely positioned and which is adapted to supply lubricant to the engine-mounted lubricant delivery tank. Such lubricating systems have particular utility in connection with outboard motors. It is also desirable to provide the operator with an indication or warning when the lubricant in either of the tanks falls below a predetermined value. For example, if the lubricant in the delivery tank falls below a predetermined value and there is still adequate lubricant in the storage tank, the operator will know that there is some fault in the system for delivering lubricant from the storage tank to the delivery tank. On the other hand, if the amount of lubricant in the storage tank falls below a predetermined value and there is still adequate lubricant in the delivery tank, the operator will know that it is time to replenish the lubricant in the storage tank, but also will be confident that there is adequate lubricant available to lubricate the engine for a period of time.
It is, therefore, a still further object of this invention to provide a lubricating system for a two-cycle internal combustion engine that embodies a lubricant delivery tank and a lubricant storage tank and means for providing an indication to an operator when the level in either tank falls below a predetermined amount.
The advantages of separate lubricating systems for two-cycle outboard motors incorporating a small lubricant delivery tank mounted internally within the cowling of the outboard motor and a remotely positioned lubricant storage tank have been stressed. Such systems should employ an arrangement for pumping lubricant from the storage tank to the delivery tank when the level of lubricant in the delivery tank falls below a predetermined amount. However, it is the normal practice to mount outboard motors for tilting about a horizontally disposed axis from a normal running condition to either a trim up or a tilted up out-of-the-water position. If the lubricant delivery tank is mounted on the outboard motor and the motor is tilted up, the lubricant in the delivery tank will flow to another orientation which may give a low level indication that could cause further lubricant to be delivered from the storage tank to the delivery tank. This would be undesirable when the outboard motor is tilted up since the delivery tank would be overfilled when the motor was again tilted down.
It is, therefore, a still further object of this invention to provide an improved lubricating system for an outboard motor which insures against the overfilling of the lubricant delivery tank when the motor is in a tilted up condition.
In conjunction with the use of separate lubricating systems and particularly those for outboard motors that employ a relatively small lubricant delivery tank mounted by the engine and periodically replenished from a remotely positioned storage tank, it is necessary to provide some arrangement for venting the area above the lubricant in the delivery tank to the atmosphere so as to compensate for changes in the amount of lubricant in the tank. Although such venting may be conveniently performed by means of a pressure responsive check valve at an upper level in the tank, the fact that the outboard motor is tiltable about a horizontally disposed axis, as aforenoted, somewhat complicates the venting arrangement. Furthermore, the fact that the outboard motor is also steerable about a vertically extending axis and may tilted up when steered to either an extreme right or lefthand position can further complicate matters. Unless the venting system is properly arranged, the tilting up of the motor can cause the lubricant to be discharged through the venting system and foul the motor and the surrounding area.
It is, therefore, a still further object of this invention to provide an improved venting system for a separate lubricating system for a two-cycle internal combustion engine.
It is a further object of this invention to provide an improved venting system for an outboard motor embodying a motor-mounted lubricant delivery tank that will insure against the spillage of lubricant regardless of the orientation of the motor.
In separate lubricating systems of the type embodying an engine-mounted lubricant delivery tank and a remotely positioned lubricant storage tank with a pumping device for pumping lubricant from the storage tank to the delivery tank, it has been the practice to mount the pump in or in proximity to the storage tank so as to insure that it will always be primed and available to pump lubricant to the delivery tank when required. If the pump is mounted externally of the storage tank and at a low level, it is likely to become contaminated and damaged by the debris which may accumulate in the bottom of the hull of the watercraft. Although these problems can be avoided by mounting the external pump at a higher level, this can itself cause problems. If the pump is not mounted at the lowest level in the tank, there may be situations wherein the pump will cavitate when the oil level in the tank falls to a point where it is at or near the level of the lubricant pump. Such cavitation can cause damage to the pump and other problems.
It is, therefore, a further object of this invention to provide an improved separate lubrication system for a two-cycle engine wherein pump cavitation may be avoided.
It is a further object of this invention to provide an improved pumping arrangement for the storage tank of a separate lubricating system of the type described that insures against damage to the pump by cavitation.
As has been noted, the mixing of lubricant with the fuel has been a well known method for lubricating two-cycle internal combustion engines. The induction systems for such engines normally cause the fuel and lubricant to pass across most, if not all, of the components of the engine to be lubricated. Thus, even if a separate lubricating system is incorporated which does not employ the mixing of lubricant directly with the fuel in the fuel storage tank, it has been the practice to inject lubricant into the induction system so that it will mix with the intake charge and be delivered to the various components of the engine. Such arrangements have the advantage of permitting more accurate control over the amount of lubricant delivered, but also have the advantage of not requiring the operator to mix the lubricant with the fuel. However, this type of induction system and lubricating system does not always insure adequate lubrication of all components of the engine.
It is, therefore, a still further object of this invention to provide an improved lubricating system for a two-cycle internal combustion engine which offers simplicity and, at the same time, insures the adequate amount of lubrication of all components of the engine.
In connection with the use of separate lubricating systems for internal combustion engines of the two-cycle type, it is normally the practice to employ some form of pump for delivering lubricant, even when the lubricant is delivered merely to the induction system for mixing with the fuel/air intake charge. However, as has been noted, the amount of lubricant required by the various components of the engine may vary.
It is, therefore, a still further object of this invention to provide an improved lubricating system for a two-cycle internal combustion engine wherein portions of the lubricant are delivered to the engine under pressure and other portions are delivered in a non-pressurized manner.